How do I change my Pokemon in unite?

Do you mean change your favorite so that it shows up at the top of your Pokemon license list and is on your main page?

Or

Do you mean how to select which Pokemon to play with in a battle/stadium?

Or

Do you mean change your pfp/icon?

Well um since you haven't answered Dragonfly's question I'll just explain all 3.

• To change your favorite pokemon, go to the pfp thing on the top-left that opens up the menu → select Pokemon and when you hover over a pokemon (or tap it if you play on mobile) there should be a small "Favorite Pokemon" toggle on the top-left.
• To select Pokemon for battling, you just go through the menu on the left of the battle screen.
• To change your pfp icon, there are little events you can do that get you different pfps, but there should be a "Customize" option in the menu, which you can use to change your pfp, background, and some other stuff.

Welp I hope that helped😊